There are many options. Have you considered installing the 200 amp main service panel outdoors, then feeding the barn with one 100 amp feeder and the basement 100 amp panel with another feeder? Many manufacturers make an all-in-one meter-base and two main breaker units.
As far as installing a separate service to the barn, check with the power company and the AHJ, many town have special rules for separate metering.
Earl